1. Field of the Invention
The present invention relates to reflecting mirrors for reflecting light, and more particularly to a reflecting mirror suitable for outdoor use.
2. Description of the Related Art
Vehicles are provided with reflecting mirrors that are so-called side mirrors (may be designated door mirrors or outer view mirrors) for viewing the right and left rear sides. Recently, such reflecting mirrors that have two layers of coatings, that is, a silicon dioxide layer and a titanium dioxide layer have been used, which are to be described below.
That is, the reflecting mirror of this type is exposed to rain since the mirror is mounted outside the cabin of a vehicle. At this time, water droplets such as raindrops adhered on the surface of the reflecting mirror would cause reflected images to be distorted. Accordingly, a hydrophilic coating composed such as of silicon dioxide (SiO2) is formed on the surface of the reflecting mirror to improve the hydrophilic property thereof and thus turn the water adhered on the surface into a thin film. This prevents distortion of reflected images caused by settlement of water droplets.
On the other hand, a reflecting mirror of this type always has a chance to have ingredients (mainly organic substances) such as exhaust gases of other vehicles, which adhere on the surface of the reflecting mirror. The adherence of the ingredients on the surface of the reflecting mirror will cause the hydrophilic property provided by means of the aforementioned hydrophilic coating. Accordingly, a photocatalytic coating composed of titanium dioxide (TiO2) or the like is provided between the hydrophilic coating and the glass surface. Thus, it is intended to maintain the hydrophilic property of the surface (that is, the surface of the reflecting mirror) of the hydrophilic coating by decomposing organic substances adhered on the hydrophilic coating by means of the photocatalytic action such as titanium dioxide near the surface of the reflecting mirror.
Furthermore, the aforementioned photocatalytic coating with the hydrophilic coating having a thickness of 20 nm or greater cannot allow the photocatalytic action of the photocatalytic coating to be effected on the surface of the hydrophilic coating. Thus, full use of the function cannot be made. On the other hand, as shown in FIG. 21, the photocatalytic coating itself having a thickness below 200 nm cannot prevent a sodium ingredient contained in the glass from being diffused into the photocatalytic coating. An experiment shows that this sodium ingredient reduces the photocatalytic action, whereby the contact angle of water droplets becomes much larger on the surface of the hydrophilic coating and full use of the function cannot be made.
However, to make full use of the photocatalytic action in consideration of the aforementioned fact, for example, the hydrophilic coating is set to approximately 15 nm in thickness and the photocatalytic coating is set to approximately 300 nm in thickness. This provides a surface optical reflectance of approximately 24% of the hydrophilic coating layer and that of approximately 35% of a chromium (Cr) coating provided on the back surface of the glass as a reflecting film. As such, the surface optical reflectance of the hydrophilic coating and the chromium coating being close to each other (that is, no significant difference between the two) would cause light to be reflected substantially likewise on the surfaces of the hydrophilic coating and the chromium coating. Particularly, as shown in FIG. 22, in terms of the spectral characteristics of light, light having a wavelength of 550 nm to which human eyes are most sensitive allows the surface reflections on the hydrophilic coating and that on the chromium coating to have substantially the same optical reflectance. This will cause a viewer of the reflecting mirror to view both of the reflected lights, which provides a double image that has the same two images slightly shifted to each other when viewed on the reflecting mirror.
In view of the aforementioned fact, the object of the present invention is to provide a reflecting mirror that prevents a double image and secures a sufficient hydrophilic property.
To achieve the aforementioned object, a reflecting mirror according to the present invention comprises a substantially transparent glass substrate having opposite sides, a reflecting film which provided on one side of the glass substrate for reflecting light incident on the other side of the glass substrate, a hydrophilic coating predominantly composed of silicon dioxide, provided on the side of the glass substrate opposite the reflecting film, having a thickness ranging from 5 nm to 20 nm, and a photocatalytic coating predominantly composed of titanium dioxide, provided between the hydrophilic coating and the glass substrate, having a thickness ranging from 220 nm to 280 nm, for decomposing organic substances adhered on of the hydrophilic coating by a photocatalytic action.
According to an aspect of the present invention, a reflecting mirror is characterized in that the thickness of the photocatalytic coating ranges from 250 nm to 280 nm.
According to another aspect of the present invention, a reflecting mirror is characterized by selectively reflecting light of a wavelength ranging from 430 nm to 490 nm.
According to another aspect of the present invention, a reflecting mirror is characterized in that the reflecting film includes a reflecting film body for reflecting incident light, and an optical thin film, for selectively absorbing light of a wavelength other than a wavelength ranging mainly from 430 nm to 490 nm, provided between the reflecting film body and the glass substrate.
According to another aspect of the present invention, a reflecting mirror is characterized in that the glass substrate selectively absorbs light of a wavelength other than a wavelength ranging mainly from 430 nm to 490 nm of transmitted light.
A reflecting mirror according to another aspect is characterized by comprising a substantially transparent glass substrate having opposite sides, a reflecting film which provided on one side of the glass substrate for reflecting light incident on the other side of the glass substrate, a hydrophilic coating predominantly composed of silicon dioxide, provided on the side of the glass substrate opposite the reflecting film, having a thickness ranging from 5 nm to 20 nm, and a photocatalytic layer predominantly composed of titanium dioxide, provided between the hydrophilic coating and the glass substrate, having a thickness ranging from 100 nm to 140 nm, for decomposing organic substances adhered on the hydrophilic coating by photocatalytic action, and a photocatalytic coating, predominantly composed of silicon dioxide, provided between the glass substrate and the photocatalytic layer, having a thickness of at least 80 nm, and including a sodium diffusion limiting layer for limiting diffusion of sodium ions from the glass substrate into the photocatalytic layer, the reflecting mirror selectively reflecting light of a wavelength ranging mainly from 430 nm to 490 nm contained in light reflected on the reflecting film before the reflected light passes through the glass substrate.
A reflecting mirror according to another aspect is characterized by comprising a substantially transparent glass substrate having opposite sides and an optical reflectane, a reflecting film provided on one side of the glass substrate for reflecting light incident on the other side of the glass substrate, a hydrophilic coating, provided on the other side of the glass substrate, a photocatalytic layer, provided between the hydrophilic coating and the glass substrate, for decomposing organic substances adhered on the hydrophilic coating by photocatalytic action, and a sodium diffusion limiting coating, having an optical reflectance less than that of the glass substrate, and located between the photocatalytic coating and the glass substrate for limiting diffusion of sodium ions from the glass substrate into the photocatalytic coating.
According to another aspect of the present invention, a reflecting mirror is characterized in that the hydrophilic coating includes a silicon dioxide layer having a thickness ranging from 5 nm to 20 nm and predominantly composed of silicon dioxide.
According to another aspect of the present invention, a reflecting mirror is characterized in that the photocatalytic coating comprises a titanium dioxide layer predominantly composed of titanium dioxide, provided between the silicon dioxide layer and the glass substrate, and having a thickness ranging from 110 nm to 140 nm.
According to another aspect of the present invention, a reflecting mirror is characterized in that the sodium diffusion limiting coating comprises a silicon dioxide layer predominantly composed of silicon dioxide, provided between photocatalytic coating and the glass substrate, and having a thickness ranging from 90 nm to 110 nm.
According to another aspect of the present invention, a reflecting mirror is characterized in that an electrochromic coating having a conductive coating which is colored or discolored by being energized or not energized is provided between the reflecting film and the glass substrate.
According to another aspect of the present invention, a reflecting mirroris characterized in that the sodium diffusion limiting coating includes a silicon dioxide layer predominantly composed of silicon dioxide, provided between the photocatalytic coating and the glass substrate, and having a thickness ranging from 70 nm to 90 nm, and a titanium dioxide layer predominantly composed of titanium dioxide, provided between the silicon dioxide layer and the glass substrate, and having a thickness ranging from 110 nm to 140 nm.
According to another aspect of the present invention, a reflecting mirror is characterized in that an electrochromic coating having a conductive coating which is colored or discolored by being energized or not energized is provided between the reflecting film and the glass substrate.
According to another aspect of the present invention, a reflecting mirroris characterized in that the sodium diffusion limiting coating includes a silicon dioxide layer predominantly composed of silicon dioxide, provided between photocatalytic coating and the glass substrate, and having a thickness ranging from 90 nm to 110 nm.
According to another aspect of the present invention, a reflecting mirror is characterized by comprising a substantially transparent glass substrate having opposite sides, a reflecting film provided on one side of the glass substrate and which reflects light incident on the other side of the glass substrate, a hydrophilic coating and provided on the other side of the glass substrate, and a photocatalytic coating, predominantly composed of titanium oxide, having a thickness ranging from 230 nm to 270 nm, provided between the hydrophilic coating and the glass substrate, for decomposing organic substances adhered on the hydrophilic coating by photocatalytic action.